\begin{tikzpicture}
    \tkzDefPoints{0/0/O}
    \tkzDefPoint(270:1.5){A}
    \tkzDefPoint(90:1.5){Q}
    \tkzDefPoint(140:1.5){C}
    \tkzDefPoint(230:1.5){P}
    \tkzDefPoint(20:1.5){m}
    \tkzDefLine[perpendicular=through A,normed](O,A)  \tkzGetPoint{b}
    \tkzDefPointOnLine[pos=2.0](A,b)  \tkzGetPoint{B}
    \tkzDefPointOnLine[pos=1.8](B,A)  \tkzGetPoint{D}

    \tkzDrawCircle[thick](O,A)
    \tkzDrawPoint(O)
    \tkzDrawPolygon(A,C,P)
    \tkzDrawSegment(B,D) %\tkzDrawLine[add=0 and 1](B,A)
    \tkzDrawSegments[dashed](A,Q  C,Q)
    \tkzMarkRightAngle[](A,C,Q)
    \tkzLabelPoints[right](O)
    \tkzLabelPoints[below](A,D)
    \tkzLabelPoints[right](B,m)
    \tkzLabelPoints[above](Q,C)
    \tkzLabelPoints[left, yshift=-.3em](P)
\end{tikzpicture}

